Iran's Revolutionary Guards said on Monday they had tested a naval weapon that could destroy any vessel in a range of 300 km, Iranian media reported.
The comments are likely to stoke tensions over Iran's disputed nuclear program after Tehran failed to meet Saturday's informal deadline to respond to a package of nuclear incentives offered by six world powers to defuse the row.
The West accuses Iran of seeking to build an atomic bomb, a charge Tehran denies. The United States has not ruled out military action if diplomacy fails to end the row, prompting Iran to warn it would target U.S. bases if attacked.
"The Revolutionary Guards have recently tested a naval weapon with a 300 km range in which no vessel would be safe and would be sent to the depths," Guards Commander-in-Chief Mohammad Ali Jafari was quoted as saying by Fars News Agency.
He said it was Iranian-built but did not give details.
U.S. forces are stationed in several countries around the Gulf, including Bahrain where the U.S. Navy Fifth Fleet is based. Iran says U.S. forces are in range of its weapons and has threatened to impose controls on shipping in the Gulf if pushed.
Around 40 percent of globally traded oil leaves the region through the Strait of Hormuz, a choke point at the southern end of the Gulf, flanked by the coastlines of Iran and Oman.
Western capitals had set an informal deadline of Saturday for Iran to freeze expansion of its nuclear work in return for a halt to measures to impose more UN sanctions.
The freeze was aimed at getting preliminary talks going, before formal negotiations on a package of nuclear, trade and other incentives start once Tehran suspends uranium enrichment, a process that can have both civilian and military uses.
Iran, the world's fourth largest oil producer, has dismissed the idea of a deadline and refused to suspend enrichment, saying it only wants to master the technology to generate electricity.
The United States said on Sunday that Iran had left the UN Security Council no choice but to increase sanctions on the Islamic Republic for failing to respond to the offer.
The incentives package was backed by the United States, Britain, France, Germany, China and Russia. Moscow opposed the idea of setting a deadline but also told Tehran not to drag its feet with any response.
Last month, Tehran test launched a series of medium and long-range missiles including some it claimed were are capable of striking Israel.
Israel speculates that the missiles tested were Iran's Shahab-3 ballistic missile and not a more advanced weapon.
Want to enjoy 'Zen' reading - with no ads and just the article? Subscribe todaySubscribe now